Our objectives focus on the study of two distinctive sets of proteins. Polymerase beta is a DNA polymerase essential in base excision repair. Anthranilate synthase and anthranilate phosphoribosyl transferase are essential to the conversion of chorismate to tryptophan. We intend to obtain a high resolution data set of polymerase beta:DNA template: primer:ddNTP mismatch complex which has proved difficult on conventional rotating anode sources. We have obtained high resolution data sets of anthranilate synthase and anthranilate synthase phosphoribosyltransferase from enterobacteriacae. We will obtain phasing information from heavy metal soaks of each complex.